Resonating Disk Density Sensor for Gas Measurement
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Solution Overview
Problem
Existing density sensors are not well adapted for measuring gas density due to insufficient sensitivity, as the resonance characteristics of the resonating element are not significantly affected by the low density of gases at atmospheric conditions.
Innovation Solution
A density sensor with a resonating disk having a large diameter to thickness ratio, made of metals like stainless steel, nickel-iron alloy, or Molybdenum, and a pedestal, coupled to a membrane and actuating/detecting module, designed to measure gas densities ranging from 30 g/m³ to 150 kg/m³, with a protective cover to prevent contamination, and a manufacturing method involving electric welding and annealing for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional resonating element is used for gas density measurement, then the sensor structure is simple, but the sensitivity is insufficient due to low gas density
Solution Approach 1:
The invention transitions from conventional paddle-shaped resonating elements to a disk-shaped resonating element with large diameter-to-thickness ratio. This dimensional change increases the surface area-to-mass ratio, enhancing the interaction between the resonating element and gas molecules, thereby improving sensitivity to gas density variations without significantly increasing structural complexity
Solution Approach 2:
The invention optimizes specific parameters of the resonating element, including setting the thickness between 25-200 μm and diameter between 4-12 mm, creating a large diameter-to-thickness ratio. These parameter changes maximize the resonating element's sensitivity to gas density while maintaining structural simplicity and manufacturability
2Measurement precision
If the resonating element thickness is reduced to improve sensitivity, then the sensitivity increases, but the mechanical strength decreases
Solution Approach 1:
The invention specifies using metal materials (stainless steel, nickel-iron alloy, or Molybdenum) for the resonating element. These materials provide high specific strength (strength-to-density ratio), allowing the element to maintain sufficient mechanical strength even at reduced thicknesses of 25-200 μm, while still achieving the desired sensitivity improvement
Solution Approach 2:
By changing from a paddle shape to a disk shape with large diameter-to-thickness ratio, the invention redistributes the mass and structural support differently. The large diameter provides sufficient structural rigidity even with thin thickness, resolving the contradiction between reduced thickness for sensitivity and maintained strength
3Reliability
If a metal resonating element with large diameter to thickness ratio is used, then the sensitivity and robustness are improved, but the manufacturing complexity increases
Solution Approach 1:
The invention replaces conventional mechanical attachment methods with electric welding to attach the resonating element to the pedestal. This substitution provides stronger, more reliable joints that enhance long-term stability and robustness, while the welding process is well-established and compatible with metal materials, keeping manufacturing complexity manageable
Solution Approach 2:
The invention specifies optimal parameter ranges (thickness 25-200 μm, diameter 4-12 mm, diameter-to-thickness ratio) that balance performance improvement with manufacturability. These parameters are chosen to be achievable with standard manufacturing techniques while delivering the desired sensitivity and robustness improvements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor achieves robustness and long-term stability, improved sensitivity for gas density measurement, and cost-effective manufacturing, suitable for demanding applications including high pressure and corrosive conditions, with enhanced metrological performance.
Implementation Method 1
As the resonating element vibrates in the fluid, some of the surrounding fluid is displaced. The effective mass of the resonating element is increased by an amount δm determined by the volume of fluid entrained by the moving section.
Implementation Method 2
the resonating element vibrates in the gas... resonance characteristics of a resonating element having a paddle shape barely change with gas composition at atmospheric conditions
Data Source
AI summary
A density sensor to measure the density of a gas having a density ranging from 30 gram per cubic meter to 150 kilogram per cubic meter and a working pressure ranging from 0 to 100 bar. The density sensor includes a resonator housing, a membrane, an actuating/detecting module mechanically coupled to the membrane, and a resonating element arranged to be immersed in the gas, the resonating element being mechanically coupled to the membrane by a pedestal. The resonating element is a resonating disk having a thickness ranging from 25 μm to 200 μm and a diameter ranging from 4 mm to 12 mm. The resonating disk extends parallelly to the membrane or being angled relatively to the membrane and is coupled by its center to the pedestal. The resonating disk is made of a metal chosen among the group comprising stainless steel, nickel-iron alloy and Molybdenum.